Prequel. The word alone usually sends right-minded humans running for the caves, their minds heaving with nightmarish images of Jar Jar Binks and Dumb & Dumberer: When Harry Met Lloyd. And yet, with Sunday's Rock and Chips, writer John Sullivan has deliberately chosen to brave the prequel minefield with a feature-length show about the early days of Only Fools & Horses' Rodney Trotter.

Rock and Chips has presumably been made with an eye to turning it into a series. And here's hoping that happens. After all, given the hopelessly misjudged Christmas specials and The Green Green Grass, it seems fairly obvious that Sullivan is determined to keep meddling with the corpse of Only Fools & Horses until it belches out another hit – and I'd rather this than The Crimefighting Adventures of Mickey Pearce.

Whether Rock and Chips is creatively successful is another matter. It opens with the sight of Joan Trotter gazing into a mirror – never a good sign – and it takes itself far too seriously for a show about the Trotter boys – one of whom will grow up to fall through a bar in a funny way. More than anything else, though, Rock & Chips gets stuck on the question that's blighted almost every prequel – is the show really necessary?

There can't be too many people eager to know what Del Boy's parents were like, or how much of a pervert his mother's old manager was, or what Granddad Trotter would be like if he was played by Phil Daniels at his most insufferable. It's a rich universe that John Sullivan is mining – even the most peripheral characters are already entrenched in Only Fools And Horses mythology – but so what? Who cares about the mythology of a sitcom?

It's a different story with sci-fi, of course. The most important ingredient for a sci-fi show is a slavishly obsessive fanbase who'll follow it to its grave – and sci-fi has those in droves. That's why Smallville is so rabidly devoured by its fans, and why the new Battlestar Galactica prequel Caprica has got the internet wetting itself with nerdish anticipation. Even Star Trek: Enterprise outlasted the original series by almost 20 episodes, and that was rubbish.

This is because sci-fi attracts a special breed of completist fan determined to uncover every single facet of the world they're watching, past and present. That's just not the case with sitcoms – people generally watch those because they just want a bit of a laugh. Fill in the gaps with a fancypants prequel if you want, but without conferences full of outfitted fans arguing about its place in the canon, it'll just make you look self-indulgent. Or, in the case of 1988's First of the Summer Wine, utterly pointless.

But even though it is self-indulgent and unnecessary, Rock and Chips still has its moments. Nicholas Lyndhurst clearly has a ball playing against type as a seasoned criminal and, on the few occasions that it tries to be funny, it largely succeeds. So maybe the prequel isn't completely dead after all.

If that's the case, what other TV prequels would you like to see? Constable Morse? Loose Teenagers? A version of Life On Mars where someone from the 1970s goes back to the 1950s? The Crimefighting Adventures of Mickey Pearce? It's The Crimefighting Adventures Of Mickey Pearce, isn't it? That's OK, I'd probably watch it too.